Investigators in the field of food technology have been witnessed to exhibit a continuing interest in the development of nutritional food products both through the utilization of often discarded food processing by-products, such as milk whey, and through the substantially direct conversion of vegetable proteins, for example the conversion of soybean material to dairy or meat substitute foodstuffs. With the former, expanded food utilization efficiencies are promised through a productive conversion of by-products otherwise wasted, and with the latter, a more direct and, theoretically, less expensive production of food products is envisioned.
Soybeans (Glycine max) have long been considered to be an important source of protein, their cultivation having originated before written record in Eastern Asia. Appropriately treated, soybean materials represent an inexpensive source of protein. In the more basic of such treatments, a soybean milk is produced, the earliest and simplest technique for its preparation involving the sequential steps of washing, soaking, grinding, filtering and boiling. Of this process, the latter step of boiling is provided to destroy trypsin inhibitor as well as to inactivate lipoxgenase, which is considered as the cause of rancidity and off-flavor. See in this regard:
I. mattick, L. R., W. F. Wilkens, and D. B. Hand. "Precursors of Volatile Off-flavor in Soymilk." N.Y. Agric. Exp. Sta. Bull. 1966 (prepublication) PA1 Ii. bourne, M. C., E. E. Escueta, and J. Banzon. "Effect of Sodium Alkalis and Salts on pH and Flavor of Soymilk." J. Food Sci. 41(1) :62, 1976. PA1 Iii. nelson, A. I., M. P. Steinberg, and L. S. Wei. "Illinois Process for Preparation of Soymilk." J. Food Sci. 41(1) :57, 1976. PA1 Iv. liang Chiu. W. C., and F. O. van Duyne. "Soybean Curd Preparation, Calcium Content and Palatability." Illinois Res. Fall 1961, p.6. PA1 V. miller, C. D., H. Denning, and A. Bauer. "Retention of Nutrients in Commercially Prepared Soybean Curd." J. Food Res. 17:261, 1952. PA1 Vi. loska, Jr., S. J., and D. Melnick. "Laboratory Procedure for Evaluating the Curd-producing Capacity of Soya Products." Cereal Chem. 27:127, 1950. PA1 Vii. wang, H. L. "Products from Soybeans--to Meeting Rising Processor Interest, Tofu Process--on a Laboratory Scale." Food Technol. 21(15) :115, May 1967. PA1 Viii. smith, A. K. Oriental Methods of Using Soybeans as Food with Special Attention to Fermented Products and Notes on Oriental Farming Practices. USDA, ARS--71-17, Northern Regional Research Center, Peoria, IL, 1961, p.19. PA1 Ix. schroder, D. J., J. I. Elliot, and H. Jackson. "Nutritional Studies on Soybean Curd Produced by Calcium Sulfate Precipitation of Soybean Milk." J. Food Sci. 38:1091, 1973. PA1 X. wingerd, W. H., S. Saperstein, and L. Lutwak. "Bland, Soluble Whey Protein Concentrate has Excellent Nutritional Properties." Food Technol. 24(7):34 1970. PA1 Xi. vaughan, D. A. Nutritional aspects of whey as a food. Proceedings Whey Utilization Conference, USDA, ARS--73-69. Eastern Regional Research Center, Philadelphia, PA. 1970 p. 78. PA1 Xii. holsinger, V. H. "The Use of Cheese Whey in Beverages." Proceedings Whey Products Conference, USDA, ARS, ERRL, Publ. No. 3779, Eastern Regional Research Center, Philadelphia, PA Feb. 1973, p. 43. PA1 Xiii. badui, S. and A. C. Peng. Nutritious new drink uses whey and plant proteins. Ohio Report 59(2):37. 1974.
The population of the Western World, not having a longstanding tradition of utilizing soymilk type products, considers the taste thereof to be somewhat objectionable, the aroma of the food being considered by that population as unpleasant (i.e. beany and bitter). This aspect of the potential food long has been considered an important problem to be solved as a prelude to acceptance in the western sector of the world population.
Approaches have been made to adjust soymilk products to the western palate, for example, it has been theorized that by asserting control over the sodium ion concentration of soymilk, an effective mechanism will be provided for improving the flavor thereof. See in this regard:
The development of a bland flavored soymilk product more suited to western taste has been described as being carried out through a blanching treatment of whole soybeans with sodium bicarbonate prior to a grinding thereof. This treatment effects an enzyme inactivation as well as a trypsin inhibitor inactivation.
In this regard see:
Additional discussion concerning the development of a taste or aroma-free soybean product is provided, for example, in U.S. Pat. No. 3,937,843.
Perhaps the most important soybean product providing protein to the Asian population of the world is a soybean curd known to the Chinese as "dow foo" or, to the Japanese, as "tofu". The production of such soybean curd follows somewhat generally accepted process steps, for example, whole soybeans are washed and soaked for a given period in cold water, following which they are ground in the presence of cold water and the slurry then is filtered. The resultant soybean milk is then steamed for about thirty minutes, cooled to a selected temperature and precipitated. The precipitant traditionally used is calcium sulfate. Following removal of the supernatant liquid, the curd usually is placed in molds and gently pressed to achieve a desired moisture content. The procedure for this process is described in more detail, for example in:
Generally, the soybean curd also is considered to exhibit a "beany" taste characteristic to western palate. This taste, as well as the texture of the curd developed, depends upon numerous factors including the soybean cultivar selected as well as the type of extraction and coagulant utilized in precipitation procedures. In the latter regard, the more common precipitation procedure provides for the addition of salts to increase the ionic strength of the soymilk solution. Alternately, acids may be introduced to the solution to reduce its pH to the isoelectric point thereof. Investigations have been carried out with respect to precipitation procedures wherein salts of strong acids such as calcium chloride, magnesium chloride ferric chloride and sodium bisulfate were utilized. Additionally hydrochloric acid has been used as an effective curdling agent.
See in this regard:
Studies of the production process further have indicated that coagulation of soybean protein by the addition of a salt represents the more difficult step in the process of curd formation. For example, the incorporation of insufficient amounts of salts or the addition of salt at too rapid a rate not only creates an incomplete precipitation of protein, but also results in a turbid suspension making it difficult to separate the precipitating protein. Additions of excessive salts result in what is considered too hard a soybean curd product. As may be expected, different salts produce differences in quality of the product, for example calcium sulfate serves to coagulate the proteins slowly to form a smooth gel-like product, whereas magnesium sulfate provides a flocculant precipitate. In the above regard, reference is made to:
The temperature present at the precipitation stage has been described as one factor which markedly influences the coarseness as well as other physical properties of the resultant curd, for example, such influence is described in the following publication:
Studies of the nutritional value of soybean curd have reported that, with the exception of the limiting amino acids methionine and half cystine, all of the amino acids essential to nutrition are present. In this regard, reference is made to the following publication:
Turning now to the noted by-product of the dairy industry, whey is the serum which remains after the coagulation of the casein and fat when cheese is manufactured. It comprises principally water and six to seven percent solids including most of the ash of the original milk, milk sugar and proteins. These proteins represent about eighteen percent of the total protein in milk and the water soluble proteins in this whey are mainly beta-lactoglobulin and alpha-lactalbumin. The two proteins together with other minor protein fractions are commonly referred to as lactalbumin. Lactalbumin is a complete protein fully available to the human body and has been recognized as being highly superior to most other proteins in animal nutrition. In this regard, reference is made to the following publications:
Cheese wheys further may be categorized as "sweet whey" or "acid whey," such categorization generally depending upon the pH valuation as the whey is removed from a cheese processing vat. Generally a sweet whey will exhibit a pH of about 6.2, while an acid designated whey exhibits a pH of about 4.7. Continued bacterial action following removal from the processing vat tends to effect a continual lowering of the pH values of whey to about 4.5, whereupon most bacterial action has been observed to cease. Of course, drying the whey as by spray drying or the like to form powders will arrest the pH value, as will pasteurization techniques and the like. The price of food-grade cheese whey, for example, with respect to the corresponding price of non-fat dry milk is of considerably lower level, for example about four times lower. As in the case of the soymilk products, cheese wheys tend to exhibit a taste or aroma characteristic not particularly acceptable to the human palate. This characteristic sometimes is described as being "raw milky."
Combinations of soybean material with cheese whey products have been proposed. Fluid acid or sweet cheese whey has been mixed with soybean flour and citrus flavoring to produce protein beverages, as disclosed in the following publication:
Further, a milk substitute product has been prepared by mixing soybean material with whey, as described in Peng, U.S. Pat. No. 3,798,339. Another proteinaceous drink developed from cheese whey, sesame and soybean milk exhibiting an increase in sulfur concentration in terms of sulfur containing amino acids has been described in the following publication: